In particular with satellite radio systems, both particularly the economic efficiency with respect to the transmitting power emitted by the satellite and the efficiency of the receiving aerial are important. Satellite radio signals are as a rule transmitted with circularly polarised electromagnetic waves on account of polarisation rotations on the transmission path. Often program contents are transmitted for example in separate frequency bands which are close together in frequency. This happens in the example of SDARS satellite radio at a frequency of approximately 2.33 GHz in two adjacent frequency bands each having a bandwidth of 4 MHz with a distance of 8 MHz between center frequencies. The signals are emitted by different satellites with an electromagnetic wave circularly polarised in one direction. Consequently, aerials circularly polarised in the corresponding direction of rotation are used for reception. Such aerials are known for example from DE-A-4008505 and DE-A-10163793. This satellite radio system is additionally assisted by the emission of terrestrial signals in certain areas in a further frequency band having the same bandwidth and arranged between the two satellite signals. Similar satellite radio systems are being planned at present. The satellites of the global positioning system (GPS) emit waves which are also circularly polarised in one direction at a frequency of about 1575 MHz, so that the above-mentioned aerial forms can be basically designed for this service.
The aerial known from DE-A-4008505 is constructed on a substantially horizontally oriented conductive base surface and consists of crossed horizontal dipoles with dipole halves which are inclined downwardly in a V shape and consist of linear conductor portions and which are mechanically fixed at an azimuthal angle of 90° to each other and mounted at the upper end of a linear vertical conductor attached to the conductive base surface. The aerial known from DE-A-10163793 is also constructed over a generally horizontally oriented conductive base surface and consists of crossed frame structures mounted azimuthally at 90° to each other. In the case of both aerials, to produce the circular polarisation the aerial portions which are spatially offset from each other in each case by 90° are interconnected so as to be shifted in electrical phase by 90° to each other. Patch aerials work in a similar manner. All these aerials according to the state of the art have a lower performance with respect to reception at a low angle of elevation.
These aerial forms are of course suitable for the reception of satellite signals which are emitted by high-earth-orbit satellites—so-called HEOS. However, in particular for satellite radio signals which arrive within a low range of angles of elevation and which are emitted by geostationary satellites—so-called GEOS—an improvement in receiving power and the suppression of cross polarisation, and the improvement of reception of vertically polarised signals emitted by terrestrial transmitters, are desirable.